s=float(input('请输入你的成绩'))
if s >= 90 and s <=100:
    print(s,'A级')
elif s >= 80 and s <= 89:
    print(s, 'B级')
elif s >= 70 and s <= 79:
    print(s, 'C级')
elif s >= 60 and s <= 69:
    print(s, 'D级')
elif s >= 0 and s <= 59:
    print(s, 'E级')
else:
    print('成绩有误')
    s = int(input('请输入你的成绩'))

